All roots, no leaf

[Hank Paloci]

Hi, I was wondering if anyone has had this experience.

As an experiment, I set up two 4 inch x 10 foot round PVC pipes with holes 6-8 inches apart and planted kale and chard. I pump water through regularly but not continually, as I lose too much heat at night. The setup looks most like NFT but I've set up the pipes so that there is always maybe an inch of water in there. The plants are in two inch net pots filled with river pebbles. There is no other media in the pipes.

I'm getting thick stalks and lots of root activity but very little leaf growth. Can you help me figure out what I'm doing wrong?

I am in SoCal and weather is probably not an issue.

My conclusion is that the plants aren't getting enough nutrients and I need to add media to the pipes. Pumping more water probably wouldn't hurt either. I'd rather not do these things because media is heavy and constant pumping brings more cost in heating water for my fish.

Note: I pipe this same water at the same intervals through a more standard GB with fully mature tomato plants that are giving me really nice fruit even in January.

Any help/comments appreciated. Thanks.